Van Allen Probes EMFISIS Waves
Chorus from 2012-10-26

The Van Allen Probes EMFISIS Waves instruments detected these signals with three orthogonal magnetic antennas (Bu, Bv, Bw) during UTC hour 20 of October 26, 2012. The main feature is an unusual variation on low-frequency chorus. Instead of the more common rising tones associated with the classic "singing birds" sound of chorus, this sample shows multiple falling tones that then curve back upward in frequency.

Chorus waves in Earth's magnetosphere are generated in the Van Allen radiation belts by electrons spiraling along Earth's magnetic field lines in this region. Once generated, the chorus waves interact with the moving electrons, either accelerating them to higher energies or disturbing the spiral orbit of the electrons and causing them to fall into Earth's upper atmosphere along the magnetic field lines.

The animation shows a frequency-time spectrogram of the data with a moving cursor that indicates the time position of the audio track.